This invention pertains to the acceleration of large numbers of ions to high energies using an intense relativistic electron beam. One of the novel features is the controlled motion of ions trapped in a deep potential depression (the virtual cathode) associated with an intense relativistic electron beam by utilizing the time history of the injected electron beam current and voltage, and by appropriately varying the drift tube radius.
The invention offers a convenient and natural method and apparatus for establishing the larger collective accelerating fields associated with an intense electron beam and extending them over relatively large distances. The method and apparatus thereby avoids the difficulties of generating high voltage RF power and the high voltage arcing problems which establish a practical limit for the accelerating fields achieved in conventional linear accelerators (the accelerator operated at the Stanford Linear Accelerator, for example). The invention allows the construction of low cost, lightweight charged particle accelerators for the production of intense, high kinetic energy ion beams.